ICT was first formed in Britain by a 1959 merger of the punched card tabulating firms of Powers-Samas and British Tabulating Machine Company (BTM). ICT later acquired several other computer-related firms and, in 1968, under government pressure to form a single British computing company to compete with the large American firms, acquired the rest of the industry and renamed itself International Computers Limited (ICL).

ICT (and ICL) were successful for a time and produced a range of machines (the 1900 and 2900 series) to compete with IBM. They were taken over by the telecommunications firm of STC in 1984 and, when STC was itself bought out, the remaining ICL assets were sold to Fujitsu.